This total extinction of sailing vessels as fighting war-ships made its effects felt across the ocean, and an attempt was made in the United States to create an efficient steam navy. With but a limited supply of funds for its creation, American architects were forced to study fully the necessities of the fleet before embarking on the new work. Since the foundation of the navy it had been always one of the principles of American construction to build ships whose measurement exceeded those of similar types in Europe. Carrying out this principle in the development of the new fleet, there appeared in 1855 four steam frigates superior in every way to any European vessels of their class that had yet appeared. The importance of these vessels did not lie simply in their excess of measurements over European frigates, but in the combination of all those parts which go to make up the efficient lighting vessel. The Imperatrice Eugènie with her 3600 tons displacement had surpassed previous frigate developments, but had made no impression on other types of vessels. On the contrary, the appearance of the Minnesota, Wabash, Colorado, and Merrimac was the signal for the disappearance of the line-of-battle ship. The displacement of these ships was about 4700 tons, or 1100 tons in excess of the Eugènie. The battery was of the same _number_ of guns as in the French ship, but exceeded by an inch in calibre that of any broadside afloat, the combination of numbers and weight giving these ships superiority even over three-deckers. Whilst the design of the Eugènie called for a speed of 12 knots, her coal supply was sufficient for but 1500 miles. The Americans, with a speed of 9½ knots, carried coal for 2500 miles. The sail-surface of these ships was enormous, ranging as high as thirty times the area of the immersed midship section. In 1858 a fifth vessel was added to this type (Niagara), the displacement in this instance being carried to 5500 tons, speed 12 knots, with a coal capacity for steaming 2500 miles, full sail-power, and a battery in which calibre had been carried to the extreme limit of broadside fire (11 inches).